Study On Operation Characteristics And Membrane Fouling Of Spiral Symmetry Stream Anaerobic Membrane Bioreactor

In recent years,the substantial increase in urban sewage discharge has seriously polluted the water environment.Anaerobic membrane bioreactors(An MBRs)as a new type of wastewater treatment technology that a hybrid system of anaerobic biotechnology and membrane separation.An MBRs were expected to achieve high strength influent and low strength effluent due to the high efficiency of anaerobic biological treatment and the effluent water quality stability of membrane separation,and have been increasingly used for urban sewage treatment.Gotten inspiration from these,our group developed a spiral symmetry stream anaerobic membrane bioreactor(SSS-An MBR,patent application no: CN201610325276.6),which consisted of the existing patent spiral symmetry stream anaerobic bioreactor(SSSAB)and an external type flat membrane module.The performances of the SSS-An MBR during start-up period and stable operation period were studied;the mathematical models for optimization of design and operation of the system were established;and the characteristics of membrane fouling and its influencing factors were discussed.The main research contents and results were shown as follows:(1)The operational performance of start-up and stable period showed that:a.The reactor was stable and efficient during the start-up period of 33 days.The p H of the reactor ranged from 6.78 to 7.44,while the volatile fatty acid(VFA)was almost undetectable and no acidification occurred.The alkalinity(ALK)was in the range of 1264.01-1639.64mg/L,and the ratios of VFA to ALK ranged from 0.001 to 0.016.The removal rate of chemical oxygen demand(COD)was stable at 90.27%-95.35%,and the average COD removal rate was 85.75%.b.The system performance with biogas aeration was slightly better than that without biogas aeration.The OLR and COD removal rate of the SSS-An MBR with biogas aeration were 2.28 kg COD/(m3·d)and 98.24 %,higher than those without biogas aeration of 2.13 kg COD/(m3·d)and 97.58 %,respectively.The coefficient of variation(CV)of the system with biogas aeration of 0.78 was lower than that without biogas aeration of 0.89,and the stability of former was higher than the latter.c.With the increase of influent COD,the effluent COD(160mg/L)and CV(0.16)in stage 1(average influent COD=2300 mg/L)of the SSSAB were significantly higher than those in stage 2 and stage 3(the average influent COD were 4500 and 8000mg/L,respectively).The effluent water quality and stability declined,but the difference of membrane effluent COD and its CV for different stages were not significant.(2)The mathematical models for optimization of design and operation of SSS-An MBR system:The mathematical model (?) among anaerobic bioreactor volume V,influent quantity Q and influent COD concentration X was established,and (?) between membranes area A and Q was obtained.They could provide references for the design and operation optimization of the similar type anaerobic membrane bioreactor.(3)The influence of biogas aeration on the operation and membrane fouling of SSS-An MBR system showed that:i.The influence of biogas aeration on the operation and membrane fouling:a.The influence of biogas aeration on membrane fouling was studied by the trans-membrane pressure(TMP)and membrane surface morphology.The rate of TMP increase of each stage with biogas aeration(0.14,1.6 and 5.5 k Pa/d,respectively)were relatively slow,and the operating cycle was half of that without biogas aeration when the same TMPs were reached.For the former a dense and thin gel layer was formed on the membrane surface,and the latter with a sparse and thick cake layer.b.Membrane fouling mechanism of the SSS-An MBR with biogas aeration was studied by extracellular polymeric substances(EPS)and its composition.For the system without biogas aeration,the total solids(19.03g/L)on the membrane surface were higher,which was the main cause of membrane fouling.For the system with biogas aeration,slime-EPS(89.38 mg TOC·(g VSS)-1)and polysaccharide(PS)were higher and the value of PN/PS was smaller on the membrane surface than without biogas aeration,which was main causes of membrane fouling.ii.The influence of influent COD on the operation and membrane fouling:a.Membrane fouling included slow fouling period and rapid fouling period.Compared to stages 2 and 3,the rate of TMP increase in slow fouling period of stage 1 was slow and long(K11 = 0.188 k Pa/d,T = 13d),and the rapid fouling stage was fast and short(K12 = 4.935 k Pa/d,T = 15d).The rates of TMP increase in slow fouling period and rapid fouling period of stage 2 were similar to stages 3.b.With the increase of the influent concentration,the viscosity of the mixed solution enabled the increase of the TMP,enhancement of the adhesion,decline of the aeration scouring effect and reduction of the flocculation effect.The increase of total EPS was mainly attributed to the increase of S-EPS and LB-EPS content,inducing the increase of viscosity of the mixture.A correlation between the PN and the viscosity of the mixture was observed,and no obvious trend was found among PS and PN / PS and viscosity of the mixture.